Bearings used for tenter clips in plastic film stretching machines require good heat resistance since they are used under a high-temperature ambient environment generally ranging from 150 through 250 degrees Celsius.
Especially, for such resins as PEEK and PI which are in increasing demand in recent years, the stretching operation is performed under a super-high ambient-temperature of 400 degrees Celsius.
In rolling bearings for use in such a super-high ambient temperature, separators made of a solid lubricant are placed between the rolling elements in order to supply lubricant by a small and constant amount at the super-high temperatures since there is no grease usable at such a high temperature as 400 degrees Celsius.
The rolling bearings which use such separators are disclosed in Patent Literature 1 and Patent Literature 2.